TRAVELLERS sometimes have to show their travel documents five times when catching a flight: at check-in, at security, then occasionally at outbound immigration, before another check when boarding. Finally there is passport control at the destination. Each is a potential queue. So regular flyers will be interested in anything that might speed up the process.

One answer could be facial-recognition technology. In the past few weeks, a number of airports have begun to introduce a system that will scan faces, match them with electronic passport photos, and allow those passengers it recognises to skip lines.

In Tokyo, the government has been trialling facial-recognition technology in two airports since 2014. It hopes to introduce the system in full in time for the 2020 Tokyo Olympics. In France, Groupe ADP, which operates Charles De Gaulle airport in Paris, began testing similar software in February. Queues at the airport have doubled since new security measures were introduced after terrorist attacks in 2015; this, thinks ADP, might be one way to ease the pain. In Canada, meanwhile, plans are in place to start rolling out facial-recognition kiosks this spring. Similar trials have also been announced in Schiphol Airport in Amsterdam.

Australia, though, has the most ambitious plans. In 2015, the government unveiled its "Seamless Traveller" initiative, which set a target of automating 90% of passenger processing by 2020, and offered A$93.7m ($71.9m) to help bring it about. Brisbane Airport recently launched a new system that could allow passengers to undergo a single biometric check-in and have no further need to produce documents before boarding the plane.

Such technology is not yet infallible. An earlier trial in Japan had to be scrapped in 2012 because it failed to identify passengers correctly 18% of the time. Success rates will surely improve. Even so, they will not be a queue-panacea. Facial recognition can confirm your identity, but it cannot scan your bag. Nor will it shorten the wait to board your flight or ease the bottleneck when passengers jostle simultaneously to put bags in overhead lockers. (And in any case, anyone who has tried existing, cumbersome automated passport kiosks may argue that little time is actually saved.)